This invention concerns the interconnection of related electronic circuit boards in a system by means of multiway edge connectors.
It is common practice to use one or more such multi-way connectors at one edge of an electronic circuit board, so that a multiplicity of signal, power and earth paths are connected simultaneously when the board is inserted into the system. Problems arise as a result of misalignment of the board and the mating halves of the connectors, and also irregularities in the contact positions within the connectors, either of which give rise to inconsistencies in the sequence in which the signal, power and earth contacts are connected together. Where electronic circuit boards using more than one power supply voltage are interconnected in a system, it is well known that semiconductor devices can be damaged or destroyed by insertion or extraction of one or more of the boards, with the power supplies switched on. To protect vulnerable semiconductor devices against damage caused by accidental removal of boards without previously disconnecting the power, protection devices can be fitted to all susceptible input and output ports. In digital systems where a multiplicity of signal input and output paths are used, a very large number of protection circuits would have to be incorporated. The need for some form of protection is imperative where low voltage, low impedance bi-polar integrated circuits are interconnected with higher voltage, high impedance field-effect integrated circuits which are very easily ruptured.